If you're looking at KenPom, the efficiency numbers are adjusted for SOS, and UNC had the number 1 SOS this year.  The four factors numbers are not adjusted for SOS while the efficiency numbers are.  Further, they did have the 63rd best TO% this year on offense, which is pretty solid.  They're not giving up many chances and creating a lot of second chances on offense.
Defensively, not quite sure what you were looking at but they were 23rd in not fouling, 59th in not allowing ORB, and 16th in defensive 2PT%.  That is certainly good.